NASA Support to the Arecibo Planetary Radar – Update 21 November 2016

NASA has, for several decades, supported the development and use of planetary radar, both at the National Science Foundation's Arecibo Observatory in Puerto Rico and at NASA's Goldstone facility in California. NASA provided financial and technical support for the initial installation of Arecibo's S-band radar in the early 1970s and for its upgrade in the 1990s. The radar has been used to investigate Solar System bodies from Mercury to Titan, and in more recent years to refine the orbits and characterize the physical aspects of Near Earth Objects (NEOs).

Planetary radar is particularly important for the study of NEOs and for the assessment and mitigation of the NEO impact hazard for Earth (see http://echo.jpl.nasa.gov and http://www.naic.edu/~pradar for further information). The more precise range and velocity information provided by radar, which enhance the positional data obtained by optical and infrared telescopes, is critical for reducing the uncertainties in the orbital trajectories of NEOs and predicting their future paths and determining possible impact events. Size and rotation characteristics may also be measured, and secondary "moonlets", if present, detected. For objects passing sufficiently close to Earth, radar imaging can constrain shape and other surface properties, almost to the precision achievable by a spacecraft flyby mission.

Keeping the mutually supportive radar capabilities of both Goldstone and Arecibo is of great interest to NASA. Because of its size and transmitter power, Arecibo can detect NEOs roughly twice as distant as Goldstone, even though the fully steerable Goldstone can see a larger fraction of the sky. Using both in a bi-static mode can achieve even higher resolution imaging. NASA has been providing support for Arecibo planetary radar operations through its Near Earth Object Observations Program, an element of its Planetary Defense Coordination Office (PDCO). This totaled about $3.6 million in FY2016. Radar observations have comprised about 500 hours of time on the telescope annually in recent years. NASA has communicated to NSF its general desire and intent to continue making use of the Arecibo telescope for planetary radar, in a similar manner and at a similar level of support, assuming that the capacity for operating the telescope as a radar facility is maintained at the present level, and provided that sufficient funding is appropriated each year by Congress. The organization managing the Arecibo Observatory under a future agreement with NSF will be requested to propose to NASA's Near Earth Object Observation Program for support of radar operations. NASA expects to support at least 400 hours per year of telescope operations allocated to planetary radar research, and at least 300 hours of that dedicated specifically to NEOs. A list of completed and scheduled NEO observations is available at http://www.naic.edu/~pradar/sched.shtml.